1. Field of the Invention
The present invention relates generally, to switch assemblies and, more specifically, to energy-harvesting switch assemblies which convert mechanical energy into electrical energy that is used to generate and transmit radio waves, encoded with circuit control signals, to a remote receiver.
2. History of the Prior Art
It is commonly difficult, costly and/or impractical to install wires between existing controlled electrical systems/circuits and new controlled electrical device(s). The level of difficulty and/or impracticality may be attributable to the need to damage or demolish ceilings, floors, or walls, in order to run control wires. Labor costs for installing new wiring can be considerable. This is particularly true if a team of electricians is required to perform the job.
The technology disclosed in this application has been incorporated into wireless control products produced by Ad Hoc Electronics LLC under the ILLUMRA trademark. Ad Hoc Electronics, a member of the EnOcean Alliance, has become the largest supplier in North America, of self-powered, battery-free, wireless lighting control and energy management systems. EnOcean GmbH of Oberhaching, Germany is a pioneer in the design and manufacture of energy-harvesting switching and sensor modules. EnOcean's primary technological contribution was the creation of wireless switches and sensors which operate with minuscule amounts of energy. As a result of this breakthrough, energy-harvesting wireless sensors, of the type produced by EnOcean and its partners, can work where those based on other technologies fail. Energy-harvesting wireless switches and sensors are prime examples of such devices. All ILLUMRA™ products operate using the EnOcean protocol, which is the de-facto standard for energy-harvesting wireless controls. The technology allows energy harvesting ILLUMRA™ transmitters to operate indefinitely without the use of batteries. The motion of a switch actuation, light on a solar cell, or other ambient energy in the environment provide power to ILLUMRA™ transmitters, providing zero-maintenance wireless devices. The ILLUMRA™ product line includes multiple products which operate in the uncrowded 315 MHz band offering greater transmission range than other wireless technologies and minimal competitive traffic.
The ILLUMRA™ hybrid control system combines benefits of ZigBee 802.15.4 Industrial Wireless Relays (IWR) from Ad Hoc Electronics with the benefits of EnOcean-compatible ILLUMRA™ Self-powered Wireless Controls. ILLUMRA™ wireless systems allow users to control electrical loads 150 feet away; the EnOcean+ZigBee hybrid system extends that range up to 1 mile. The system is made up of two component groups: first, an IWR pair designed to provide simple long-range remote control; and second, ILLUMRA™ battery-free wireless light switches and sensors, which are designed to provide easy-to-install light control and energy management systems. Together, these products make up the ILLUMRA™ hybrid system which provides simple, customizable, long range wireless light control, security control, pump station control, electronic sign control, traffic control, factory automation, and more. The hybrid system is especially effective for controlling loads across large open spaces where it would be preferable to not run wire. Examples of such applications include: barns, guest-houses, sports stadiums, tennis courts, boat-houses and garages.
The focus of the present invention are improvements to energy-harvesting switch assemblies. A standard single-rocker, mechanical-energy-harvesting switch assembly is made up of five components: a back plate or carrier; an energy-harvesting module (i.e., the electrical generator, signal encoding circuitry, and radio transmitter) that fits into a recess in the back plate or carrier; a face plate; a rocker; and a retainer clip which holds the entire assembly together. There are three significant problems associated with conventional mechanical-energy-harvesting switch assemblies.
The first problem is that the energy harvesting module—or modules for a multi-switch assembly—are easily removed from the switch assembly by prying off the rocker and popping off the retainer clip. Once these items have been removed, the face plate and the energy-harvesting module can be removed. This is potentially a very expensive problem, as each energy-harvesting module retails for about $100. That fact coupled with the existence of no-questions-asked selling forums, such as the eBay® auction website, makes these devices attractive targets for thieves.
The second problem is related to the use of modules employing two different radio transmission frequencies. Whereas energy-harvesting modules manufactured for the European market typically employ a frequency of 868 MHz, those manufactured for the U.S. market typically employ a frequency of 315 MHz. Given that the components designed for the U.S. market have a much lower operational frequency, a longer antenna is required. That longer antenna is unable to fit within the module itself. There is currently no provision for neatly installing a longer antenna within the switch assembly.
The third problem relates to wear of the rocker where it contacts the spring-loaded energy bows of the energy harvesting switch module. The energy-harvesting switch module has first and second parallel ferromagnetic plates, which are in intimate contact with opposite poles of a tiny cylindrical neodymium-iron-boron (NIB) permanent magnet. A U-shaped ferromagnetic core rockable between the two parallel ferromagnetic plates passes through a solenoid wound on a bobbin. The generation of an electrical pulse requires the application of pressure on the appropriate side of the rocker. When a threshold pressure is reached, which is determined by the magnetic attraction of the permanent magnet to the first ferromagnetic plates, the bow snaps and the ferromagnetic core attaches itself to the second parallel ferromagnetic plate. The snap causes a reversal of magnetic flux in the core, which induces a first current pulse in the solenoid. The first energy pulse is used to transmit a radio signal containing multiple redundant data packets. Different data packets are encoded depending on which switch pad on the energy-harvesting switch module is pushed. Multiple circuits can be controlled by a single module and data packets can include a control signal for each circuit. At a remote receiver, these data packets are decoded to create control signals which establish or modify circuit function in some manner. When the pressure is released, a coil spring causes the ferromagnetic core to snap back to the first ferromagnetic plate, thereby generating a second energy pulse as the bow returns to its original position. The second pulse can be used to generate a secondary signal which can be used, for example, to implement a dimming function for the circuit. The bows, which are designed to operate for tens of thousands of cycles without failure, are typically made of composite plastic materials having a high fiberglass content. The abrasive nature of these composite materials is responsible for rapid wear of the contacting edges of the rockers.